At the Greenlane Country Club, Neil Klugman holds Brenda Patimkin’s glasses so that she can swim. He finds her beautiful, and later he asks his cousin Doris for her name and decides to call her. No one picks up the phone at her house on the first call, and though his Aunt Gladys teases him, he calls again after dinner. She answers this time, and they make plans for him to pick her up from tennis later that night. Leaving Newark for the suburbs, Neil notices the stark differences between the city and its wealthier, more spread-out surrounding communities.

Neil finds Brenda at the tennis courts, playing with a friend. He watches her play a few sets and notices that she only rushes the net after it grows dark. After the match, they go for a walk, and Brenda tells Neil, who attended Rutgers, that she will be returning to Radcliffe in Boston that coming autumn. When he questions her about her style of play, she explains that she only rushes the net after dark because her friend is less likely to hit it back hard without being able to see well, and she wants to protect her nose job. Neil believes that she is a snob, but they share their first kiss.

The next day, Neil is back at the country club as Brenda’s guest. When she asks him to join her in the pool, he gives her glasses to Doris, who complains that he did not thank her the day before and questions why he doesn’t move to Arizona with his parents. In the pool, Neil and Brenda kiss underwater, and he touches her breasts. They spend the whole day in the pool, their feelings for one another growing stronger. Brenda’s brother, Ron, meets them in the pool and challenges them to a race. Neil declines, and Brenda leaves to call their mother and tell her Neil will join them for dinner.

At the house, Neil sees a different life from his own at home. The Patimkins do not eat in the kitchen one by one but are served their meals at their table by their servant, Carlota. They have a big backyard with lots of sporting equipment, where Brenda and Neil sit after dinner while she tells him of her strained relationship with her mother. She tells him that her mom does not let her spend money because she thinks they still live in Newark and need to save. This comment about life in Newark angers Neil, but before an argument breaks out, Mr. Patimkin asks Neil to take his place in a game of basketball with Julie, Brenda’s younger sister. He lets Julie win.

Neil arrives 20 minutes early for work at the library and walks through Asbury Park. Three years prior, he attended a Rutgers branch based in an old bank in the park, and as he passes it, he realizes how much he loves Newark. He arrives at the library, a job he does not expect to have forever but is afraid will drain him before he is ready to move on.

A Black boy comes into the library and asks for books with pictures of hearts, and Neil sends him upstairs. Soon after, his coworker comes down to complain about the boy, worried that he will wreck the books, and rather than summon their boss, Neil goes to check on the boy. The boy is marveling at Gauguin paintings, and while Neil sees no problem, he knows that the other librarians want to throw him out.

Neil arrives at the Patimkins’ house, and Brenda tells him he must stay and watch Julia while everyone else brings Ron to the airport. Neil resents the role of babysitter and snoops around the Patimkins’ house after they leave. He goes to the basement and finds a bar full of unopened alcohol bottles and a fridge full of fruit. Julie surprises him by the fridge and looks at him as though she thinks he stole something. They play ping-pong, and Neil decides not to coddle her. As he beats her, she gets angry, accusing him of cheating, and storms off. Brenda and her parents return, and that night, Neil and Brenda make love for the first time on the living room couch.

The boy comes to the library every day to look at the Gauguin book, and Neil even stops someone from taking the book out, telling them there is a hold on it. He wants the boy to be able to keep reading it, despite knowing his actions could cause problems with his boss. For the next week and a half, Brenda and Neil spend every night together, making love on the couch. One night, they go swimming at the country club, and Brenda asks if he loves her. Though Neil says no, she assures him that she wants him to. They play a game of surprise, in which one person waits on a chair with their eyes closed while the other swims until they come back and surprise the other. With each round, Neil becomes more afraid that Brenda will leave. At the end of the game, he finally declares his love for her.

They spend the rest of the summer together, taking drives, raiding the fruit fridge in the basement, and spending time with Brenda’s tennis friend. Neil begins to notice that the Patimkins are indifferent to him, but Brenda convinces her father to let Neil stay at the house for a week during his two-week vacation from the library. On his final day at the library before this vacation, Neil hears that he will get a promotion upon his return. Later that day, the man looking for the Gauguin book returns, and Neil rudely dismisses him, telling him that it is still unavailable. When the boy comes in that day, Neil tries to get the boy to sign up for a library card so that he can take the book home, but the kid declines, saying that it will get ruined by his family. As he drives to Brenda’s house, Neil grows nervous that his plot to keep the Gauguin book in the library will be discovered and that he will lose his job, though he knows he shouldn’t care, as he believes the library is not his career.

When Neil arrives at the Patimkins’ home, Brenda tells him that Ron proposed to his girlfriend, Harriet, and they are to be married on Labor Day. After dinner, Neil unpacks in the guestroom, and Ron visits. Neil notices that he seems ambivalent about getting married. Neil hears Brenda and her mother fighting downstairs over Neil’s presence in the house, but soon everyone leaves, and Neil and Brenda have the house to themselves. Brenda complains about her mother, and Neil asks if he should leave. Brenda wants him to stay and takes him to a spare room with all the family’s old furniture from Newark. She searches for money her father once hid and told her to find in an emergency, but its secret place is empty. She wanted to take it, tear it up, and put it in her mother’s purse to show her they are no longer in Newark. Looking at the old furniture, Neil imagines them out on their own, living a new life. They make love on the old couch.

Over breakfast, Brenda decides they should go to the local track and run a half mile. Brenda wants Neil to train for a mile, and each morning, he runs while she times him. At night, he and Brenda sit in their separate rooms reading until Ron goes to bed and Neil can sneak into her room. One night, Neil hears Ron play a record, Goodbye, Columbus, and as he sleeps next to Brenda, he dreams that he is the captain of a ship and that the boy from the library is his first mate. They are leaving a Pacific island while Black women on the shore throw them leis and call out “Goodbye, Columbus” to them. Each blames the other for leaving the island, as neither Neil nor the boy wants to leave.

As the week with the Patimkins ends, Brenda convinces her mother to let Neil stay another week. On the day that Harriet is due to arrive, Neil is left alone in the house. Neil begins obsessing over the end of the summer, as Brenda will leave for college at the end of the week, on the day after the wedding. He does not know what this means for him or whether the relationship will continue. Brenda returns to the house alone, as Harriet’s flight is delayed. In an attempt to bring them closer together, Neil suggests she get a diaphragm. She does not want to, and they argue for the first time. Neil wounds Brenda by accusing her of wanting to end the relationship. They avoid each other for the rest of the day.

That night, Harriet arrives, and Neil watches as Mrs. Patimkin fawns over her future daughter-in-law in ways she never does over Brenda. He also watches as the family accepts Harriet while continuing to ignore him. As the family turns in for the night, Neil goes to Brenda’s room and accuses her of not wanting the diaphragm because she doesn’t want to be with him.

The next morning, Brenda goes shopping with Harriet, and Neil is alone in the house with Mrs. Patimkin. He senses judgment when she asks if his mother is involved with Hadassah like she is and he doesn’t know. She suggests he join B’nai Brith, like Ron, but he commits to waiting until marriage until he does so. When she invites him to Temple with the family, he cannot answer as to whether he is orthodox or conservative, and he feels her judgment grow. They begin to discuss how Brenda is not as traditional as her mother when the phone rings. Silver patterns have arrived at Patimkin Kitchen and Bathroom Sinks, but Mrs. Patimkin needs them immediately. She sends Neil with her Volkswagen, even though he offers to take his car, to the store to retrieve them.

When Neil arrives at the Patimkins’ store, he sees Ron helping his father run the business. Mr. Patimkin calls Neil into his office and comments that Ron isn’t great at his job but that it is a family business, before sending Neil on his way with the silver patterns. Neil takes a detour to visit a deer sanctuary nearby, and while there, he begins to wonder why he loves Brenda. He returns to the Patimkins’ house, where he finds Brenda modeling her new dress for Harriet and her mother. They tell her she ought to be the bride but make no mention of who would be her husband. Later, Brenda brings Neil outside, where she says she called the Margaret Sanger Clinic for a diaphragm but hung up when they asked if she was married. He offers to take her to New York City for one, away from anyone she might know.

Neil and Brenda go to New York City, and he waits outside the doctor’s office. To pass the time, Neil goes into a church and pretends he is praying, asking God for clarity on whether or not he loves Brenda. After the appointment, she meets him on a bench and tells him she has the diaphragm, and he proclaims his love for her. As the wedding approaches, the house descends into chaos. One night, Ron invites Neil to listen to records. He plays Goodbye, Columbus, a commemorative record from his graduation at Ohio State University. It details the football games and even Ron’s last introduction to a basketball game. Neil sees how enraptured Ron becomes, and as he leaves, he thinks of Ron as his brother-in-law after his union with Brenda through the diaphragm.

The day of the wedding arrives, and while Brenda and the rest of the family dance, Neil finds himself with Leo, Mr. Patimkin’s half-brother, who talks about his wife and child constantly. During a gap in the dancing, Neil finds Brenda and her father, who hints to Neil that he can marry Brenda and join the family business. The night goes on, and Brenda gets very drunk. She disappears into the bathroom, and Leo reappears, saying that Neil and Brenda will be the next couple to be married. Leo rants about his job as a lightbulb salesman and his inability to make a lot of money like his brother does. Neil suggests to him that he and his family go home, as they are the last people left at the wedding, and they depart with kind words for him. Neil finds Brenda asleep in the lobby. He wakes her, and she follows him to the car. They get home around dawn, and the next day, Neil brings Brenda to the train at noon, and she returns to college.

Autumn is cold, and Neil feels lost without Brenda. They struggle to keep in touch, as their written and phone communications are inconsistent. Neil returns to the library and is scolded for withholding the Gauguin book. He is not punished, but the boy who came to see the book never comes again. Brenda initially tells Neil that she is coming home for Rosh Hashana, though he is disappointed when she calls him a few days later and says she cannot make it due to schoolwork. Despite his work schedule, Brenda convinces Neil to take the train to visit her. His boss does not want him to take Rosh Hashana off, but when Neil hints that his resistance could be seen as antisemitic, he relents.

Neil arrives in Boston but finds that there is a new emotional distance between himself and Brenda. They check into a hotel, and Brenda tells him that her mother found the diaphragm. Both parents wrote her letters, and she shows them to Neil. Her father’s letter reached her first and makes no mention of the problem other than a warning not to listen to her mother. He tells Brenda that he mostly blames Neil but forgives Brenda and even encourages her to buy herself a coat for the harsh Boston winter. Her mother, however, judges her to be an ungrateful child who betrays her parents. Mrs. Patimkin looks down on Neil in the letter, confirming his suspicion that she always disapproved of him.

After Neil reads the letters, he accuses her of intentionally leaving the diaphragm home to be found. She denies it and insists that she cannot go home now because of her parents’ judgment. Neil dismisses her concerns, saying her parents will never forsake her. He asks Brenda what is next for them. Brenda does not give Neil a clear answer about their relationship but tells him that she cannot bring him around her parents. He accuses her of wanting to leave him throughout their time together, and she calls out his paranoia. They soon realize that they both refer to their love for each other in the past tense, and they break up. Neil leaves Brenda crying on the bed, and as he walks across Harvard Yard, he stops and looks at his reflection in a window, wondering what made him pursue and love Brenda in the first place. As he stares, he sees through his reflection and sees a wall of books, poorly shelved. He gets on a train and is back in Newark at dawn, with enough time to get to work.